This invention relates to cargo handling systems that facilitate movement of cargo into and out of cargo carrying vessels such as ships, barges and aircraft. More specifically, this invention relates to a cargo ramp that is easily stowed onboard a cargo carrying vessel and easily extended from an elevated cargo opening to the surface of cargo handling areas such as a runway, the ground, various loading platforms and docks or quays to provide for the loading and unloading of cargo of various descriptions, including large, heavy self-propelled vehicles.
In the prior art, various ramp arrangements have been proposed for movement of cargo between a cargo carrying vessel and a cargo loading and unloading zone that is at a higher or lower elevation than the cargo deck of the vessel. Basically, such prior art cargo arrangements can be categorized as those which form a portion of the cargo carrying vessel, those which are stored or maintained at a cargo loading and unloading facility and those which are carried onboard the cargo carrying vessel and deployed as the need arises. The cargo ramp of this invention falls into the latter category and, in many respects, provides various improvements over and alternatives to the cargo ramps disclosed in my previously issued U.S. Pat. No. 4,039,163, which is assigned to the assignee of this invention.
U.S. Pat. No. 4,039,163 discloses cargo ramps arranged for storage within the cargo compartment of an aircraft wherein each cargo ramp comprises two or more hinged together ramp sections. Each of these cargo ramps includes a wheel assembly that is mounted to the lower terminus of the ramp assembly for supporting the lower end of the cargo ramp during portions of deployment and retraction sequences in which the cargo ramp is moved outwardly from or inwardly toward the aircraft. During such deployment and retraction sequences, the upper end of the cargo ramp is supported by a first set of deployment fittings that are located along the outside upper edges of the ramp and include rollers that are engageable with guide channels which are mounted on the floor of the aircraft cargo compartment. When the cargo ramp is deployed, a second set of deployment fittings, which are located along the upper edges of the cargo ramp, are engaged with sill fittings that are located below the outer edges of the aircraft cargo opening to securely lock the upper terminus of the cargo ramp to the aircraft.
Although the cargo ramps disclosed in U.S. Pat. No. 4,039,163 and various other prior art cargo ramps are fairly satisfactory in facilitating loading and unloading cargo of the type for which they are intended, there are several areas which remain open for improvement. For example, prior art cargo ramps that are designed for stowage on the cargo carrying vessel generally are configured for use with only a single type of vessel, e.g., ships or aircraft, and often are designed for use with a particular configuration of one of these types of vessels. A cargo ramp having more universal application is desirable both from the standpoint of manufacturing economics and to attain a certain degree of standardization. Further, although various cargo ramps such as those disclosed in U.S. Pat. No. 4,039,163 can be constructed to facilitate large heavy cargo such as wheeled or tracked vehicles that are driven or pulled into and out of the vessel, such prior art cargo ramps are not intended to accommodate extremely heavy construction equipment and military weapons systems that have gross weights in excess of 100,000 pounds and/or single axle load weights as much as approximately 35,000 pounds.
It can be recognized that configuring a cargo ramp for use with extremely heavy cargo and various cargo vessels such as aircraft and ships renders various design constraints more burdensome and introduces various additional constraints that are not met by prior art structure. In this regard the cargo ramp must not only be as light as possible and be configured for rapid operation between the extended and stowed positions, but must accommodate changes in vertical distance between the vessel cargo deck and the surface of the cargo loading and unloading zone. For example, when such a cargo ramp is utilized on a ship or other seagoing vessel variations in tide affect the vertical distance between a cargo deck of the vessel and the surface of a pier or quay. Such variations in vertical distance can also be encountered with a cargo carrying aircraft of the "kneeling" variety wherein the aircraft landing gear and support system is operable to decrease the distance between the aircraft cargo opening and the surface of the runway.
Certain deflections and movement of the cargo ramp and vessel must also be accommodated. First, when cargo of substantial weight is moved upwardly into or downwardly out of a vessel, forces are exerted on the ramp and vessel that can cause rather slight but not insignificant vertical displacement of an aircraft on its landing gear or a ship in the water. Loading and unloading operations can also cause substantial forces to be exerted in a horizontal direction. For example, if a heavy vehicle must be stopped suddenly as it is proceeding down such a cargo ramp, the interface between the upper end of the ramp and the vessel can be subjected to substantial tension.
In addition to the forces and movement caused by the passage of heavy cargo, a suitable cargo ramp arrangement must withstand forces and movement resulting from environmental conditions. For example, with respect to aircraft cargo ramps of the general type disclosed in the previously mentioned U.S. Pat. No. 4,039,163 wherein the ramp extends forwardly and downwardly from a cargo opening within the nose section of the aircraft, near hurricane conditions have been experienced which caused approximately 0.75.degree. of yaw between the ramp and the aircraft. Ramps configured for use with large cargo ships are subject to similar forces and movement in that, although cargo ships suitable for carrying cargo such as large wheeled or tracked vehicles are of substantial size, heavy winds and seas can cause pitching and rolling movements and attendant forces on the cargo ramp and vessel. Unless a cargo ramp is configured to withstand all of the various movements and forces mentioned, large concentrations of force can occur within the cargo ramp-vessel interface region and structural failure can result.
Certain other aspects must be considered in configuring a cargo ramp of the above described type. In this regard, to provide maximum versatility, such a cargo ramp must not only be designed for rapid deployment and storage, but it is also desirable to provide a configuration that can be employed for loading and unloading at relatively unimproved cargo handling facilities. For example, with respect to both ships and aircraft, there is often a need to supply large construction equipment and/or military systems to regions which do not have smoothly surfaced cargo handling zones or to supply such equipment to a cargo handling facility that has been damaged through natural disaster or other causes. Additionally, such a cargo ramp should also be constructed for ease of operation during deployment and stowage and should require a minimum number of operating personnel.
Accordingly, it is an object of this invention to provide a cargo ramp suitable for use with cargo carrying vessels such as aircraft and ships wherein the cargo ramp facilitates the loading and unloading of heavy cargo such as large vehicles and equipment.
It is another object of this invention to provide a cargo ramp of the above mentioned type wherein the cargo ramp is configured for stowage within the vessel and for rapid deployment therefrom.
It is yet another object of this invention to provide a cargo ramp of the above mentioned type wherein the ramp can be employed for loading and unloading cargo at relatively unimproved cargo handling facilities.
Still further, it is an object of this invention to provide a cargo ramp of the above mentioned type that exhibits relatively low weight relative to the cargo ramp load handling capabilities.
Even further, it is an object of this invention to provide a cargo ramp that can be readily stowed and deployed by a minimum number of operating personnel.